Computers (along with smartphones, PDAs and similar devices) play a prominent role in Homestuck. They are used for chat clients, and to run the Sburb / Sgrub software
Trollian is the troll version of Pesterchum, the name likely a reference to the real-life Trillian instant messenger client. Its users "troll" each other, and like Pesterchum, users choose pseudonyms, called "trolltags." In the trolls' cases, these generally relate to their associated zodiac sign or other defining trait. Together with the Kid's handles, their abbreviations comprise all sixteen possible combinations of genetic bases.
Trollian features a ChumpRoll, a similar sort of Rolodex to Pesterchum's ChumRoll. When Karkat, TereziSburb Logo and KanayaSburb Logo use Trollian, they themselves are listed on it in addition to all the other trolls. Whether this is a part of Trollian or their personal preference is unknown.
In Hivebent, Karkat tries out the beta version of Trollian in order to talk to the other trolls, all of whom seem to already have it.